Vehicles that utilize an endless drive member such as a belt or chain to transfer power are known. For instance, lawn mowing vehicles often use an endless belt routed through a sheave or pulley system to transmit power from a drive sheave, typically attached to a crank shaft of the mower's engine, to one or more driven sheaves located, for example, on a cutting deck of the mower. The driven sheave may, in turn, be connected, e.g., via a secondary drive belt and pulley system, to spindle sheaves operatively coupled to cutting blades beneath the deck (alternatively, the belt powered by the driven sheave may directly engage the spindle sheaves, e.g., a single-belt configuration). Thus, during operation, the drive sheave may selectively drive the spindle sheaves and, thus, the cutting blades.
Typically, an idler sheave is provided with the pulley system to tension the slack or loose side of the drive belt. Tensioning of the drive belt provides various advantages including, for example, providing proper friction between the drive belt and the associated sheaves. Accordingly, belt slippage may be reduced. Tension applied by the idler sheave may also reduce excessive slack in the belt, thereby reducing the chance of the belt becoming disengaged from the sheaves during operation.
Conventional idler sheaves may rotatably attach to an end of an idler arm that pivots about an idler pivot joint. Tension is provided by, for example, an extension spring having one end fixed to mower structure and the other end operatively coupled to the idler sheave. The tension in the spring may force the idler sheave against the belt, thereby tensioning the same. The idler pivot joint may include a housing pivotally secured to the mower with a fastener. Sleeve or roller bearings may be provided to journal the housing relative to the fastener and permit the desired pivoting motion.
While effective, such idler pivot joints have drawbacks. For example, the pivotal motion experienced during operation of the idler pivot joint may be of relatively low angular displacement. As a result, localized premature wear of the sleeve or ball bearings may occur, especially where an adequate lubrication schedule is not observed. To reduce the chance of premature localized failure, manufacturers of some commercially-operated lawn mowing equipment may recommend lubricating idler pivot assemblies frequently, e.g., as often as once a day.
Moreover, operation in dusty or debris-filled environments (as may be common in some lawn mowing applications) often results in debris entering the pivot joint and contaminating the bearing interfaces. Such contamination may result in increased bearing friction, potentially accelerating localized wear and premature idler pivot joint failure.